Floor covering rubber composition



Patented July 15, 1952 UNITED STATES PATENT orrlcs 2 ,(i03,668 H FLOOR COVERING RUBBER COMPOSITION" Roelof Houwink,Wassenaar,'and Wybrand'Johan 3 Karel Schiinlau, Haarlem, Netherlands; assign- V ors to Rubber-Stichting, Delft, Netherlands No Drawing. Application August 5, 1949, Serial No. 1 8,86 theNetherlands August 6,1948

'- The invention relates to a process for the-manuat room temperature or at a slightly elevated temperature, a 5 amountsof woo d flour or similarfinely divided The principal object of the present inventionis material ofvegetable origin affects the Vulcan-,- to provide a method for the manufacture of preization with vultra- -acceleratorse unfavourably, shaped rubber articles at room temperature .or at Using, a. vulcanization temperature, at which-a a slightly elevated temperature, Another object mixture containing vulcanization ingredients inof the invention isto provide.v a. process for the 10 cluding an ultra accelerator will vulcanize within manufacture of rubber articles from cruderubaiew hours,thesamemixture-containing a '1 her whichdoes not require the use of heavy and atively large amounto twood-flour will not s expensive vulcanizin'g apparatus. Other objects any sign oiv IcaniZ i n f rsveralweeksiund' of the invention include the provision of a rapid the same. conditions, ,Apparently,. the ultraf- [5-1, and economical process for the manufacture of celerators are inactivated by theipre'senc. of "a rubber articles suitable as floor or wall covering largeamountof finely divided'inaterialgofvegeg materials. 1 tablelorigimor oiparticularconstituentsthreof;

It is well known that rubber articles can be pro- Even at the. temperature, wh'ichlis generally used duced from amixture containing, aside from rubwhen compounding rubber on the mill, the'activher and vulcanizing ingredients,, l arge quantities ity of the ultraacce1erators.is.,diininishedlinsuch of fillers such as whiting, kaoline and the like. aedegree by the presence. of relatively large Such fillers are usually added to make a cheaper, amounts of woodflour orlsimilar. materials that product, while sometimes they can confer special scorching can easily be avoided. properties on the final product. Cheap fillers It has also been discovered that the activity of which are often usedinclude: wood flour, ground theultra-accelerators, in the vulcanization of rubcorlg shredded straw and similar. finely. divided bcrlat. room temperature or at a slightly elevated wastematerial of ,vegetable origin. I I temperature can still further be enhanced by the Whenproduci 'ig', rubber-article's froin's'o'lid rubaddition of certain amines. Surprisingly, ,howbjer lsuch 'ascrepe or sheetrubber, if desired conever, we havedisoovered tha'tlthe addition of fac taining vlarge amountsloffillers, th .inixture has ti vating amines to the rubber mixture iciontainealways been shaped-and vulcanized by the appliing vulcanizationingredients. including anultracationof heat and pressure in a suitable vulcanaccelerator and Ya relatively large amount of finely izing press. f'Ih'e known compounds containing divided. material ofvegetable origin does not'ac; wood flouhor a vsimilar,finely,dividedfibroussubs celerate the vulcanization duringuthe, c mmune stance of vegetable origin; necessitated'alsoasiming p oc s in Sueh a degiethat scorchin can ilar vulcanization process; to produce a useful not be avoided, but that 'the Subs quent vulcaniproduct. Thisvulcanization step using expensive zation of the readily compounded and shaped machinery rendered the product, which should be mixture a roomitemperature Or at slightlyelee cheap because of its composition, ex-pensive; vatied temperature,isisufficiently acceleratedtc'be fit is also known to-co'mpose a rubbermixture 40 technically'aDD iQ b1Q-. l ,i which willvulcanize at-a low temperature-by-in- In the opera i n of "the process of "the p eluding special accelerators, which are-usually invention, rubber is mixed on any suitable macalled ultra-accelerators, withthe mixture.-- The chinjery ith a relatively l ge amount of fillers use of ultra-accelerators i's- 'esp'e'cia-lly advanta including'finely divided fibrous material of'vege geous when the rubber which is used as a starting 5 table origin in an amount of between l00 and300 material is in such a shape that the compounding per cent by weight calculated on the rubbe and. ingredients can be mixed with the rubber without with vulcanizing ingred e including anultrathe application of heat, e. g. by dispersing the accelerator. An amine is also incorporated'with'. ingredients in rubber latex and coagulating the the mixture, as well as a softener, pigment, and: mixture. If, however, the compoundingyoflthe otherfsubstances which may be usedto impart. rubberihvolves a step in which the mixture is' 1 special r p ti s upon the fi a p T heated,ultra-accelerators should not be used' be-Y re d ly compounded mixture, while still infitsi cause the vulcanization is accelerated byzthe. plastic state, is thereupon moulded to-itsbfinaj heatingfand scorching can not beavoided'. Thus, shape nd allowed to vulcanize at r'opmtempefa it has not been possible to mix vulcanization-in- 3'Claims n (01. 260- 750) redients including an ultra-accelerator" with solid rubber in a mill or in a mixer of'the Banb'ury,

type, because too much heat is developedduring; this process. It has been discovered that the presence of large ture or at a slightly elevated temperature, withl outth application of pressure.

ly the order of mixing which we prefer.

Example 1 I I Mixtures A and B were prepared containing the Mixture d, which contained no fibrous filler and no amine, could only-be prepared on a laboratory mill, using special precautions to avoid scorching.

The mechanical properties of the vulcanized compositions produced'from the mixtures a, b

and c are: V

I Tensile strength kg./cm. 40-50 Hardness Shore A 85-90 Elongation per cent -20 following ingredients (all parts are by weight) j i Rubber (smoked sheet) 100 100 zinc oxide. 5 5 ozocerite. 2 2 k801il16 100 100 wood flour (60 mesh) 150 150 pigment (iron oxide) 5 accelerator '(Robac Gamma) 2 dibutylamine 2 sulfur 4 These mixtures contain together all the necessary ingredients, but are separately unable to vulcanize under the circumstances prevailing during the-compounding. Equal parts of the mixturesA and B are 'thereupon mixed together,

whereby the'colourr imparted by thepigm'erit shows whether the mixture has become 'suflicIi e ntly homogeneous. The mixture is then sheeted out on a calender into a sheet of the desired thickness, which is rolled upon a bobbin and storedinithe vulcanization chamber. The hardness of the material was tested after regular time intervals by means of a Shore A durometer, and vulcanization was assumed to be completed when a hardness of. '85 was reached. This was obtained in about four weeks; I T

The time after which this was reached at various temperatures appears from the following table:

4 weeks.

Temperature of vulcanizatiomnll time'of vulcanization 3-4 h.. 23 days The=1001parts of kaoline are added to decrease still further the cost of the'mixture; they can bereplaced by equal or smaller amounts of whiting, microdolomite, hard or soft'rubber makers clay, or upito 175 parts of barytes or other inert. I mineral fillers; without-influence on" the proper ties of theflfinal product; I 7 7 Example 2 V example illustrates the manufacture'jof rubber'farticles, using .variousamounts of inert V The product from mixture d had a much lower hardness and a higher elongation.

Example 3 v This example illustrates the use of various ultra-accelerators; in a composition containing di-normal butylamine as an activator. 'The mixture consists of:

Rubber 100 Zinc oxide 5 Kaoline 100 Wood flour 200 Ozocerite 2 Stearic acid l Pigment v .2 Sulfur 2 Di-n-butylamine 2 Ultra-accelerator 1 Vulcanization completed after-- Accelerators used hours days weeks I at C. at40C. M20 0.

zinc di-butyl dithiocarbamate, 3 2 2 zinc diethyl dithlocarbamate, '2 3 6 zinc dimethyl dithiocarbamate '5 4 l .8 zinc ethyl phenyl dithiocarbamate. 2 2 5 zinc pentamethylene dithiocarbamate. 5 6 8 piperidine pentamethylene dithiocarbamate. 4 3 4 zinc isopropyl xanthate 2 1 4 Robac gamma (mixture of xanthates)- 3 2 3 I The mixtures were calendered and vulcanized at various temperatures. as shown. Experiments have revealed that the hardness as measured with ashore A durometer, can be used as an efiective indicator for-the "degree of vulcanization. A hardness or unitsindicates thatthe vulcanization has been completed, the other-mechanical properties liaving'reached their opti mum value after. about the same vulcanization I time as is needed to reach this hardness, I I

nnersi" "Mixtures were prepared containing the I following ingredients, inpartsby weight; f

a b c h dd:

. o E oHrtoonovcno Example 4 51 71 examp illu t e th 1 11 8} of a oi'ii amines as; activators in the mixture containing our preferred 5 ultra-accelerators, zinc dibutyldithiocarbamate (A) and Robac :Gammaj B), showing the influence of}; the; basicity of the amineused; I r I The following mixtures were tested: I

rubber Robac Gamma accessed I parts- 7 p I amine used 1004) at 70 rubber none. 48 1 di-n-..butyIamine;. 2." 3' triethenulamine-. 2, 6 3

The the shows the time af ter'whichvulcanrzation was. completed.

hasinsuificient activatingeflect'.

Itfis, evidentthat there are numerous factors" which, will influence conditions for. the most satisfactory operation of the present invention,,

thea'ctual limits of which cannot be established exceptby aidetailedt study of each. set ofstartihg materials and the intermediate and finished,

products. involved. The vulcanization time. can still' further be reduced by increasingjthe temperature up to 70 C., or still"higher, but the special advantages of theprocessof our. invention are not longer obvious, when, the vulcanization temperature surpasses considerably 50 C.

It is remarkablethat-a.smooth and sufficiently dense surface of the finished article produced according-"to our invention can be 'obtainedb'y calendering only, whereas until now it hasal'ways been regarded necessary to vulcanize the articles under pressure to produce a similar appearance.v The use of too high a vulcanization temperature, though causing a considerable: decrease, .in ivul1- canization time, may give rise to the formation o'fgblisters or other irregularitieson the surface, when no pressure is applied during the heating.

The ultra-accelerators which can be used in the process of the present invention are the com.-

I Pyridine, having? the lowest dissociation constant offthe amines tested,

mercially available acceleratorswhich are'known to be able to vulcani'ze a rubber mixture at'ro'om temperature, or at a slightly elev'ated temperature. Examples of such ultra-accelerators. are the dithiocarbamates, such as zinc dialkyl. d'ithiocarbamates which are available with methyl,

,but is;alsoo'bjectionabie'becauseoffthedisagr able odour ofjthese comprm'nds Examples, of amines whicr'iare suitable in the process ofthez-j considerably'reducedi, a? mixture contamihgrzincf dibutyldi-thibcazrbamate as?- an ultraeaccel'eratofi requires about days. to rea'oh the" desired' haxfd ness-;,f whereas mixturescontaihing" other: accel erators-usuall'y require about 3or-more1days; j :j

' The amines required in 'ourfprocess are pref-f. erably the-organic amines havin'gja low volatilityand a basicityigreaterfthan I'D-f Thatern'is" b'as icityff is. used to denote" thez fir'st""dissociati-on constant of the compound in aqueous solution. Experiments have shown that the aimineshfil g5,

a basici'tyipf less than" 1'0" have lessactiom while" the use of volatile amineshas" thedis'advanta'ge,

art'off the amine" escapes duringthe mix-,- latilizatibn; 1 This causes msslm present invention are" dinorrnaii butylamin6',.., ethanolamine; triethylenetetramine and ami ,ethyl? ethanol amine; Our experiments have shown th'at everyamine which satisfies thecondie tions mentioned above can be used asan activator in the process of our invention} The amine. ;is" preferably added in anlamounthbr'respondlh with: from about. 4' to. If} ,inoljs. "per,v l'fipjkgs; of rubheryor: about I to er cent. bylweiehlflisel -1 late'djonthe rubber; H

j heffinel'y'dividedffibrousfiller rquiiedl H process of'lour. invention. is preferably woocli.flour,.

whichis inexp'ensive.andfeasilysobtainable "Haw-1+.

ever; ;othe r substancesfof vcgetableorigin, uci'i" as;hashed strawjground cork flcotton lintersfandlj the like; canjal'so be, used, I An; amountiof; fibrous,

filler at least equalling the amount'of'rubber ethyl and butyl, standing for alkyl, and zinc penta' methylenedithiocarbamate, and zinc alkyl phenyl dithiocarbamate. Also the accelerator known as Pip-pip, which is piperidine pentamethylene dithiocarbamate, canbe used as an ultra-accelerator in the process of the present invention. Othersuitable ultra-accelerators are the xanthogenates such as zinc isopropylxanthate, zinc ethylxanthate, dithiobutylxanthate, and the accelerator Robac Gamma, sold by Robinson Brothers, Ltd, and believed to be a mixture of zinc salts of various xanthates.

Though all the ultra-accelerators mentioned above appear to be useful in the process of the present invention, we prefer to use the zinc dialkyl dithiocarbamate, more specifically the zinc dibutyl dithiocarbamate, as this accelerator appears to give the fastest vulcanization at room temperature. It has been established by a num- 'ber of experiments that a mixture vulcanized according to the present invention with the ultraaccelerator zinc dibutyldithiocarbamate requires about 2 weeks at C. to reach a hardness of 85 Shore A, whereas the other known ultraaccelerators require times up to several weeks 1onger to reach the same hardness. By vulcanizing at about 40 C.-this vulcanization time can be should be used, whereby very desirable properties are obtained in the final product; A smooth surface is obtained by calendering only, and the use of pressure during the vulcanizing is entirely obviated. Moreover, the sheets of compounded and calendered material can be stacked or the sheet can be rolled upon itself without any intermediate layer of separating material. being necessary. When the vulcanization is effected at a temperature below about 50 C. the cured sheets can be separated from each other without causing damage to the surface. Furthermore, the fibrous'material aids in processing the mixture as set forth hereinabove.

An upper limit to the amount of fibrous filler used is put by the fact that a rubber mixture containing more than about 300 or 350 parts of filler can be handled only with difllculty, We prefer to use an amount of between 150 and 200 parts of fibrous filler, together with up to parts of inert mineral filler, for every 100 parts of rubber.

The rubber articles manufactured according to our invention are not only cheap because of the use of an inexpensive filler and a cheap production method, but when used as a floor covering material they possess the added advantage that they need not be adhesively secured to the un-.

derlayer, because this floor covering material comprises a considerable amount of fibrous'filller, does not creep, as does a rubber floor covering material containing substantially no fibrous filler.

sure.

It is recommended to add solid, wax-like sof teners to the mixture, which aid in improving the surface layer of the material. Without these softeners, the surface appears to be easily damaged by scratching with a hard object; the scratchesv formed are only diflicult to remove. By mixing with the composition from one to several per cent of a solid wax-like substance having aclimited solubilityin the rubber at room temperature,

this dis vantage "is entirely, eliminated. It is believed t the thin layerof wax-hire softener whicljgforms onthesurfacegof thewrubber artiing th vulcan zation tr.stoymgproteasmge' surcata ac t hix l Su a s te ere Q ]PF ;P Yin -aF l g P n ve mperature vaseline and beeswax-Ya Also quantity of severalfp'e r bent is necessary' to i t"theldesired'fpropertiesto the surface'layer'. theticfigubber, or a reclaimed rubber, I as .yulcanization'characteristics similar to those ofnatiiralrubber, cjanbegusedinstead of natural -1-'ublc'ierv in' the. p roces's' lofr invention, l elzra'mpleliof a s rname synthetic r'ubberiis lymerizing .butadiene bawax appears to b'irseful, though of 'this em; styrene. when as Satisfactory re -f suits are 'bbtainle'diby replacing, up 'toQSO', percent qf lh if llbb er by: reclaimed rubber, moreover, the rubber can be wholly; o'rin partreplaced byflthe cheaper inferior grades of plantation f rubber, such/as blankets. I II tweblaimfis 1 v 1 "a mout ca I 'fiexib1e, removable, non,- creepgscratch resistant fioor covering comprising snsmerra-nnxturedr rubber, about 100-, to 300% V xii 'e ar filler 'seleq edi fr om' the group consisting, ikao.1in;- Whiting and microdolomite, about1% of an ultra-accelerator, aboutj l to 3% of a-;2jto

'bon mine of aww l tilitv and. havingia .basicity greater than 10 about 1 to 5% of a solid softener, and sulfur, vulcanized at a temperature of to C. in-the absence of pres- 12. A smooth, dense, flexible, removable, noncreep floor covering comprising a hardened mixture of rubber, about 150 to 200% of at least one finely divided fibrous vegetable material selected" from the group consisting-of wood flour and straw, about of ana inert mineral filleryf about-1% of an ultra-accelerator, about;1- to;3%

of a 2 to 8 carbon amine of low volatility an'd hav ing a basicity greater than 10-?1, and sulfur, vu1 canized. at a temperature ,of 20," to 50 1in the absenceof pressure.

.31 A"sinooth, denSeQfieXibIe', removable, 'nim;

creep, scratch resistant floor covering. comprising ahardened mixtur'eof rubber, about'150jto 200% of 'a'tjleas't' one finely divided, fibrous'vegetable material selected from the group consisting .of wood Z flour "and straw, about 100% of' kaolin; about 1 of an ultra-accelerator, about 1 063% of a 2 to 8 carbon amine of w volatility' and h'avingf a basicitygifeate'r than 10-5, and sulfur,

vulcanized at a temperature of 20 to 50j C."

the absenceoi pressure; ROE QF HOUWINK.

WYBRANQ .IIOHANIKAREL v sig ij vL U.

A QR EFE RENCES "e IT ED Q The-following references are of record in the fileof this patent: 5

" UNITE]? STATES, PATENTS w F R iGNe N- s mb 1 c u t y awe-1:.

423,308; g fGreaQtBritain Jan. 30, 193;

OTHER REFERENCES 

1. A SMOOTH, DENSE, FLEXIBLE, REMOVABLE, NONCREEP, SCRATCH RESISTANT FLOOR COVERING COMPRISING A HARDENED MIXTURE OF RUBBER, ABOUT 100 TO 300% OF AT LEAST ONE FINELY DIVIDED FIBROUS VEGATABLE MATERIAL SELECTED FROM THE GROUP CONSISTING OF WOOD FLOUR AND STRAW, ABOUR 100% OF AN INERT MINERAL FILLER SELECTED FROM THE GROUP CONSISTING OF KAOLIN, WHITING AND MICRODOLOMITE, ABOUT 1% OF AN ULTRA-ACCELERATOR, ABOUT 1 TO 3% OF A 2 TO 8 CARBON AMINE OF LOW VOLATILITY AND HAVING A BASICITY GREATER THAN 10-5, ABOUT 1 TO 5% OF A SOLID SOFTENER, AND SULFUR VULCANIZED AT A TEMPERATURE OF 20* TO 50* C. IN THE ABSENCE OF PRESSURE. 